D-Amino acids may serve as intermediates for producing .beta.-Lactam antibiotics, such as penicillin or cephalosporin; insecticides or pesticides. The conventional synthetic amino acids are generally racemized mixtures containing dextro- and levo- amino acids which should be separated by optical resolution to obtain D-form and L-form amino acids.
Among those conventional methods of optical resolution for obtaining the D-form or L-form amino acid, an enzyme method is found to be most economic and feasible by utilizing the high stereo specificity of the enzyme for the resolution of D-form and L-form amino acid. Similarly, a D-aminoacylase of high stereospecificity may also be utilized for making D-amino acid.
M. Sugie and H. Suzuki had reported in their publication, entitled "Purification and properties of D-aminoacylase of Streptomyces olivaceus", Agri, Biol. Chem. 42:107-113 (1978), the preparation of D-aminoacylase by the bacteria of Streptomyces olivaceus. From Table II of M. Sugie's publication, a relative hydrolysis rate of N-acetyl-L-Met to N-acetyl-D-Met is calculated to be: 60/689=9% as summarized in Table 4 of this application. Also, K. Kubo, T. Ishikura and Y. Fukagawa disclosed a process for making D-aminoacylase by Pseudomonas sp. 1158 in their publication entitled "Deacetylation of PS-5, a new .beta.-lactam compound II, Separation and Purification of L and D amino acid acylase from Pseudomonas sp. 1158", J. Antibiotics, 33:556-565 (1980). From Table 3 of Kubo's publication, a relative hydrolysis rate of N-acetyl-L-Met/N-acetyl-D-Met is calculated to be: 10.3/100=10.3% also summarized in Table 4 of this application.
However, the D-aminoacylase made from either Streptomyces olivaceus or Pseudomonas sp. 1158 shows poor stereospecificity, capable of hydrolyzing N-acyl-L-amino acid such as N-acetyl-L-methionine to thereby reduce the yield of D-amino acid when made by a resolution process.
The present inventors have found the drawbacks of such conventional enzyme method for making D-aminoacylase and invented the present method by using bacteria of the Alcaligenes faecalis species.